Lightweight aircraft which have been outfitted with twin pontoons for operation from lakes and rivers must be removed from the water during heavy winds or moderate wave action to prevent overturning or damage to the craft. Unlike most boats which are designed for relatively rough water, the pontoons for aircraft are designed as light and stream lined as possible so that the aircraft can fly as efficently as possible. This means that the pontoons are just barely able to keep a maximum loaded plane afloat. It is not uncommon for passengers loading and unloading to get their feet wet, even standing on a pontoon.
Because the pontoons are made from lightweight thin materials, dragging a seaplane up on a beach to get it out of the water often damages the very expensive pontoons.
At present, there are no lifts which are suitable for lifting a light seaplane from the water, which are supported by stanchions driven into the lake or river bed. Present lifts which are designed for boats do not have the structure to support the pontoons yet enable the propeller to be free of obstructions.
In addition to seaplanes, a wide variety of watercraft require lift mechanisms that can be positioned below the water line and then lift the craft above the water level. Such craft include twin hull boats, and one man motorized craft known as "Ski-doos."
Boat lifts have been found to be inadequate to meet the needs of seaplane owners who wish to quickly and easily lift these planes out of the water and launch them with the same ease and speed. The need for lifting ease and speed requirements may range from simple convenience to necessity in coping with difficult conditions induced by high waves, fast current or high winds.
Further, the present boat lifts are capable of raising a boat only a few feet while many lakes and dams may periodically rise and fall five, ten or even fifteen or more feet due to hydroelectric power generation and re-generation by refilling the lake during off peak power generation hours. Rivers and flood control dams or sea coast waterways subject to tides can rise and fall several feet and render all but the largest lifts useless at low water conditions.
The increase in the number of seaplanes, twin hull boats and ski-doos and the need to maintain clear channels has made it impossible in many locations to install the prior art devices which are set on the bottom of the lake or river and remain submerged in the water when not lifting a boat. Such apparatus is a hazard to other boats and cannot be used where a clear channel is required.
Finally, probably none of the above prior patented lifts can operate in water as shallow as the lift of the present invention.